The method for manufacturing pneumatic tires for automobiles and other vehicles is well known in the art. The general method employed is to build up the tire on a cylinder or other sort of drum shaped base that is generally collapsible to release the product upon completion. The product is then unvulcanized and typically in a shape that is known as a "green tire" or a "band". In order to become a final product tire, the unvulcanized tire band is altered by a controlled deformation or expansion or radial distention from the cylindrical or semi-toroidal form to the full toroidal or tire shape that is commonly known. During the shaping process of a tire, the tire bead portions are moved toward each other to a pre-determined spacing, the tire tread portion is moved outwardly to define the maximum diameter, and the connecting wall portions are moved together from vertical to become substantially horizontal. Achieving this shape and structure, it is necessary to allow the various components in the tire band structure to stabilize, adjust or acclimate to their changing orientation in a very precisely controlled manner. Not only is it important to control temperatures and pressures on the outside of the tire band, it is also important to control pressure and temperature on the interior of the tire band.
The general method of curing a tire band or uncured tire is to place the tire band into the lower mold half of a press, where an inflatable rubber bag is inflated inside the tire band. This inflatable rubber bag is generally referred to as a bladder and is usually made from butyl rubber and mounted on a movable stem, commonly known as a center post, which is positioned coaxially to the lower mold half. Simultaneously, the tire is inflated into a "doughnut" shape and a mold is created by the registration or occlusion of upper and lower mold halves that encase the tire band. The tire band is then cured and shaped by heat that is applied through the mold, particularly through the heat platen, and by steam pressure into the bladder. Generally, excess rubber is allowed to escape through weep holes provided in the mold, and after a time, a completed tire is formed. Before the mold is opened by reseparating the upper and lower mold halves, the bladder is deflated. Once the mold halves are separated, an unloading mechanism is used to strip the now-cured and shaped tire from the lower mold half, where the tire will rest. Once the tire is removed, a new uncured tire band can be positioned by the loading mechanism and the process begun anew. In a multiple cavity tire press, these steps are performed simultaneously for a plurality of tire bands.
The teaching of how to generally prepare tires in such a press can be learned well by just studying the patents of Leslie E. Soderquist. Some of these patents include U.S. Pat. Nos. 3,222,724, 3,260,782, 3,298,066, 3,336,630, 3,336,635, 3,336,636, 3,541,643, and 3,564,649, all of which are incorporated by reference herein as if fully recited.
As will be appreciated by studying the prior art, the curing of tires requires heavy mechanical components to counter the extreme forces produced in vulcanizing a tire. In a tire press, the respective upper and lower half molds that envelop the uncured tire and define the curing cavity must be pressed together under a squeeze load provided by a top beam and a bottom beam connected via a pair of side links or other means. If a single tire is to be formed in a press, the deflections of the top and bottom beam caused by this mechanical squeeze can be minimized, or at least made symmetrical. In fact, U.S. Pat. No. 4,453,902 to Imbert, discloses a method whereby a set of three triangulated side links can eliminate malocclusions of the upper and lower mold halves caused by beam deflections. The industry, however, clearly prefers multiple cavity tire presses for smaller tires, such as those used for automobile and light-truck service, and even if single cavity presses were to catch on for these tires, there still exists a large number of multiple cavity presses in which any opportunity to minimize malocclusion of the upper and lower mold halves due to beam deflection is still desirable.